How the land is made and changes

Science
Grade 6

Looking at a cliff, or at samples drilled out of the ground, shows that land is made of layers of gravel, sand, mud, and volcanic ash piled one on top of another. Fossils, the traces of living things from long ago, are sometimes found in these layers. Layers form when soil carried by running water settles at the bottom of a sea or a lake, sorted by the size of its grains, or when ash from a volcano piles up. Land also changes through eruptions and earthquakes, and a strong force can break the layers apart and make a fault. Because eruptions and earthquakes can change the land and cause disasters, being prepared for them matters.


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